Materials and Methods:
This is a single-center, retrospective cohort study that was approved by the Institutional Review Board at Ochsner Medical Center, New Orleans, LA. This retrospective study involving human participants was in accordance with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
Echocardiograms saved in the institutional database (Cardiovascular Imaging System, New Orleans, LA) between 2007 and 2016 were screened with the keywords of MS, MAC, rheumatic, or diastolic doming of the anterior mitral valve leaflet. We obtained demographic and clinical data from electronic medical records (EPIC, Verona, WI, USA), including age, body mass index, gender, history of diabetes, hypertension, chronic kidney disease (eGFR < 60 mL/min per 1.73 m2), ESRD on dialysis, prior radiation exposure, coronary artery disease defined by either history of acute coronary syndrome or abnormal ischemic evaluation, and history of chronic heart failure. Survival and mortality data were obtained retrospectively from electronic medical records in July 2020.
Based on echocardiographic findings, DMS was defined in our study with the presence of severe MAC that extends onto the leaflets causing restricted leaflet mobility and LV inflow obstruction. Eligible studies had at least mild MS reported by transthoracic echocardiogram with a mean TMPG of ≥ 4 mmHg. Patients with prior mitral balloon valvuloplasty, ejection fraction < 50%, heart rate ≥ 100 bpm, severe aortic stenosis, and more than mild MR or mild aortic regurgitation were excluded. Patients with RMS who met inclusion and exclusion criteria were used as the comparison group. A total of 64 patients with DMS and 24 patients with RMS met the initial inclusion criteria. We excluded patients with ESRD (6 in DMS and 1 in RMS group) for analyses related to valve area and pressure gradient because of possibly increased gradients due to high flow state and volume overload.
Echocardiography studies were performed according to the American Society of Echocardiography guidelines using either GE Vivid E9 and E95 ultrasound system (GE Vingmed, Horten, Norway) and reviewed and verified by a Level III-trained echocardiographer.17–19 MAC severity in the DMS cohort was scored as reported in Movva et al.6 The MVA by continuity equation (MVACEQ) was used as the independent reference and calculated with the following equation: MVACEQ(cm2) = (LVOT diameter)2 x 0.785 x (VTILVOT / VTIMV).11.
Continuous-wave Doppler imaging of the MV from the apical four-chamber view was used to obtain the peak and mean TMPG, as well as the velocity-time integral (VTI) of the MV. Peak E (early diastolic velocity), peak A (late diastolic velocity), and deceleration time were measured with pulse wave Doppler of the MV inflow at the MV tips in the apical four-chamber view during diastole. The LV outflow tract (LVOT) diameter was measured in the parasternal long-axis view (inner edge of the septal endocardium to the inner edge of the anterior mitral leaflet in mid-systole). The LVOT VTI was measured by tracing the instantaneous dense modal velocities throughout the systole of the LVOT pulse wave Doppler sample taken 1 cm below the aortic valve in the apical long-axis view. LVOT stroke volume (SV) was calculated with the following equation: SVLVOT (cm3) = 0.785 x DiameterLVOT2 x VTILVOT. The DMSI was calculated as follows: DMSI = VTILVOT / VTIMV (Figure 2 ). Three cardiac cycles were averaged for Doppler-related calculations for patients in sinus rhythm and five cardiac cycles for patients in atrial fibrillation (AF). A level III trained echocardiographer repeated all of the measurements for the study purposes. Two separate level-III trained echocardiographers performed the interclass correlation analysis.